— You ought to have called her yesterday .    — Yes , I know I ____ . 

The policeman _______ that the drunk driver get out of his car.

She________the opportunity，but unfortunately she just let it go.

Mike is often absent from class.” “Tell him he _________ answer for it if he goes on behaving like that.”

It has been announced that all the students ______ put on the masks before going to school in case they are infected with SARS virus.